1. Field of the Invention
The present invention relates to an in-circuit emulator having a memory management mechanism which performs a memory protection by dividing a memory area of a microprocessor into a plurality of areas of a layered structure, and more specifically to such an in-circuit emulator which can perform an on/off control of a trace on the basis of the layer number (called "execution level" hereinafter) of the memory area.
2. Description of Related Art
Conventional in-circuit emulators for a microprocessor, which perform a memory protection by dividing a memory area of the microprocessor into a plurality of areas of a layered structure, can perform an on/off control of a trace on the basis of various conditions including an address and a status. However, since information concerning the execution level is not included in a trace on/off condition, it was not sure where the execution level had changed. Therefore, it was a matter of course that it is not possible to trace only a particular execution level.
Specifically, in the conventional in-circuit emulator for a microprocessor having the above mentioned memory management mechanism, since information of the execution level is not directly from an emulation microprocessor, even if the emulation microprocessor executes a program in which an execution level changes in the way, information concerning where the execution level had changed will not be in a trace data. In particular, when an operating system (OS) and an application program are executed, it is an ordinary matter that the operating system is a high place of execution level and the application program is a low place of execution level. In this case, when only the operating system or only the application system is debugged, it was not possible to trace each or one of the execution levels, separately from each other.